Iridium-containing reforming catalyst and use thereof

ABSTRACT

An iridium-containing catalyst, particularly one comprising platinum, iridium, and palladium composited with a porous inorganic oxide base, is found useful in hydrocarbon conversion reactions, particularly reforming (hydroforming). A naphtha or straight run gasoline can be contacted with such catalyst at reforming conditions in the presence of hydrogen to improve the octane quality of the naphtha or gasoline.

Mitchell, III

IRIDIUM-CONTAINING REFORMING CATALYST AND USE THEREOF Howard LeeMitchell, 111, Baton Rouge, La.

Inventor:

Assignee: Exxon Research and Engineering Company, Linden, NJ.

Filed: Oct. 29, 1973 Appl. No.: 410,710

References Cited UNITED STATES PATENTS 8/1958 Webb 208/139 9/1959 Stineet a1 208/138 July 29, 1975 3,109,038 10/1963 Myers 208/139 3,173,8563/1965 Burton et al 208/138 3,410,789 11/1968 Ransch 208/139 3,554,902l/1971 Buss 208/138 3,655,747 4/1972 Sennewald et a1. 252/466 PT PrimaryExaminer-Delbert E. Gantz Assistant Examiner-James W. l-lellwegeAttorney, Agent, or Firm-L. A. Proctor [5 7 ABSTRACT Aniridium-containing catalyst, particularly one comprising platinum,iridium, and palladium composited with a porous inorganic oxide base, isfound useful in hydrocarbon conversion reactions, particularly reforming(hydroforming). A naphtha or straight run gasoline can be contacted withsuch catalyst at reforming conditions in the presence of hydrogen toimprove the octane quality of the naphtha or gasoline.

33 Claims, 1 Drawing Figure c 1- PRODUCT YIELD (VOLUME 7,) W

PATENTEU M29 1975 GRAPHIC DATA DEPICTiNG RUNS CONDUCTED WITH PARAFFINICAND NAPHTHENIC FEEDS, RESPECTIVELY, COMPARING -CLQNVENTIONAL REFORMINGGATALYSTj AT OPTIMUM CONDITIGNS WITH CATALY5T5 OF TI'II5 INVENTION AT5ULFUR CONCENTRATIONS OF IO REM. AND 0,4 REM.

/CATAI.Y5T I) (0. 1 rams) BAYTOWN VIRGIN MPHTI'IA FEED CATALYST ACATALYST D (1.0 RRI'Lj) CATALYST D 114 ems) CATALYST a ARAMCO NAPHTHAFEED CATALYST A CATALYST A i l l l l I AROMATIC5 lN 65+ PRODUCT (VOLUME70) (& RON) IRIDIUM-CONTAINING REFORMING CATALYST AND USE THEREOFCatalytic reforming (i.e., hydroforming) is an established process inthe petroleum refining industry and has been used for improving theoctane quality of naphthas and straight run gasolines for many years.Catalysts used in catalytic reforming are recognized as dualfunctional,perhaps more accurately polyfunctional, the catalyst composite includinga component comprising a metal, or metals, or a compound or compoundsthereof, providing a hydrogenation-dehydrogenation (hydrogen transfer)function, isomerization function, hydrocracking function, and/orhydrogenolysis function, and an acidic component providingisomerization, cracking, and/or hydrocracking functions.

The platinum group, or Group VIII noble metals (ruthenium, osmium,rhodium, iridium, palladium and platinum), despite their expense, havebeen long recognized as particularly efficient hydrogen transfercomponents. Platinum per se has, in fact, proven par excellence as ahydrogen transfer component and, in fact, possesses a combination ofproperties which makes it particularly suitable as a component forcommercial reforming catalysts. Conventional reforming catalysts havethus long employed platinum composited with an inorganic oxide base,particularly alumina, to which halogen is added to supply theisomerization function. Platinum catalysts have achieved world-wide usein commercial reforming operations.

Iridium-containing catalysts, i.e., catalysts comprising iridiumcomposited with a porous inorganic oxide, have been widely disclosed inthe literature as useful for a variety of hydrocarbon conversionreactions, viz., reforming, hydrogenation and dehydrogenation,isomerization, hydrocracking, alkylation and dealkylation, steamreforming, and the like. Iridium has also been used in combination withother noble and non-noble metals and composited with inorganic oxidesfor use as hydrocarbon conversion catalysts. Such composites have thusincluded iridium in combination with such other metals as, e.g.,platinum; tungsten; platinum and rhenium; platinum and tin; platinum,rhenium and tin; platinum and lead; platinum and zinc; platinum andthallium; platinum and indium; platinum and lanthanides; and platinumand ruthenium. Some of these catalysts have been specifically describedas useful in catalytic reforming, or hydroforming.

There is a desideratum in the art, occasioned in large part by thewithdrawal of alkyl lead compounds based on ecological considerations,and intensive efforts are again underway to improve the octane qualityof naphthas and gasolines, without use of such additives, or byelimination of such additives, by improving reforming catalysts.Improvements have been made, and new species of catalysts have beendeveloped. Despite this, platinum yet maintains a rank of distinction asa component of commercially viable reforming catalysts. Recently, e.g.,the industry has turned to catalysts which employ bimetallic componentsto provide effective hydrogen transfer for improving the octane qualityof naphthas and gasolines in commerical operations; and even morerecently, attention has turned to multimetallic catalysts, or catalystswhich contain three or more hydrogen transfer components, for use in themanufacture of commercially viable reforming catalysts. While iridiumper se has not proven outstanding as a hydrogen transfer component foruse in commercial reforming, the combination of platinum and iridium hasproven particularly effective, surpassing platinum per se as aneffective hydrogen transfer component for commercial reformingoperations.

Surprisingly, catalysts comprised of composites of platinum and iridiumwith an inorganic oxide base, particularly alumina, suitable inhydrocarbon conversion reactions, particularly reforming were reportedmany years ago, and described in U.S..Pat. No. 2,848,377. Such catalyst,however, did not achieve commercial significance, perhaps due to anumber of drawbacks. For one thing, the catalyst is verysulfur-sensitive and readily deactivated by high sulfur feeds. Moreover,the initial activity of these catalysts is very high, and serious lossof activity occurs quite rapidly due to an acute tendency of theiridium, when exposed to oxygen at elevated temperatures, toagglomerate, and even to form iridium oxide in admixture with theagglomerated metal. The activity of such catalysts is substantiallylowered as a result of the descreased surface area of the metals.Recently, however, it has become practical to regenerateiridium-containing catalysts by redispersal of the metal and, for thisreason, inter alia, platinumiridium catalysts have achieved a positionof eminence in the present art of catalytic reforming.

Platinum-iridium catalysts possess outstanding activity for use inreforming operations, activity being defined as that property whichimparts the ability to produce aromatics, aromatic production (or octaneimprovement) generally being measured as a function of temperature, feedrate, etc. Platinum-iridium catalysts also possess good selectivitywhich is defined as that property which imparts the ability of thecatalyst to produce high yields of high octane number C5 liquid productswith concurrent low production of normally gaseous hydrocarbons, i.e., C-C hydrocarbons, or solid carbonaceous by-products, and coke, which formon the catalysts during reforming. These catalysts also possess goodstability or activity maintenance, i.e., activity plotted as a functionof time, good stability or activity maintenance being defined as highretention of good activity and selectivity, or continued high activityand stability for prolonged periods during hydrocarbon conversion, orreforming operations.

While any commercially viable reforming catalyst must possess theseproperties to a significant degree, no catalyst used in real worldoperations can possess all of these properties to the Ultimate degree.One of these characteristics may be possessed by a catalyst in admirabledegree, but the poor quality of another of these characteristics mayadversely affect the worth of the catalyst. Thus, a catalyst whichpossesses good selectivity does not necessarily have good activity, andvice versa. A small decrease in C; liquid yield can thus represent alarge debit in commercial reforming operations. Conversely, the worth ofa catalyst which possesses high selectivity may be jeopardized by theconsiderable capital cost which necessitates large charges of noblemetals containing catalysts. Proper balance between these severalproperties is essential in the commercial world and an improvementgained in one property, or characteristic, cannot be too much offset byloss in another if the catalyst is to prove commercially viable.

Platinum-iridium catalysts have been shown to possess outstandingactivity, and good selectivity. Iridium,

however, is not a plentiful metal and quite expensive. For this reason,inter alia, it is desirable to decrease the amount of iridium employedon the catalyst without significant decrease of the high activity andselectivity of such catalysts. Moreover, it is desired to furtherimprove the basic platinum-iridium catalyst to the extent possible.

Accordingly, it has now been discovered that a catalyst comprisingcatalytically active amounts of platinum, iridium, and palladiumcomposited with a porous inorganic base, notably alumina, is moresulfurtolerant, more active, and has greater selectivity for producinggasolines at reforming conditions than, e.g., a catalyst otherwisesimilar except that it does not contain palladium. In fact, suchcatalyst has better selectivity than a catalyst otherwise similar exceptthat it does not contain palladium and has an even higher concentrationof iridium. Moreover, the activity of such catalyst closelyapproximates, or approaches, that of higher iridium-containingcatalysts, and at certain conditions has activity as good as higheriridium-containing catalysts. A preferred catalyst composition of suchcharacter comprises from about 0.05 to about 3 percent platinum,preferably from about 0.1 to about 1 percent platinum, from about 0.05to about 3 percent iridium, preferably from about 0.1 to about 1 percentiridium, and from about 0.0001 to about 2.5 percent, preferably fromabout 0.0005 to about 0.15 percent, and more preferably from about0.0050 to about 0.050 percent of palladium, based on the total weight(dry basis) of the composition. Preferably, also, the sum total of theplatinum and iridium contained in such catalyst compositions ranges fromabout 0.3 to about 1 percent, and more preferably from about 0.45 toabout 0.70, based on the weight (dry basis) of the total catalystcompositions. In the more preferred compositions, the atom ratio ofiridiumzpalladium ranges from about 1:1 to about 40:1, and preferablyfrom about 2:1 to about :1, whereas the atom ratio of theplatinumziridium ranges from about 0.25:1 to about 5:1, and preferablyfrom about 1:1 to about 2:1. The absolute concentration of the metalsused, particularly the iridium and palladium, has a relationship to theatom ratios employed, as does the nature of the feed and the amount ofsulfur and nitrogen contained in the feed. In general, the higheriridium content catalysts (i.e., those containing 0.225 wt. percent lr),for best results, require greater concentrations of palladium,particularly when processing highly paraffinic feeds, and conversely thelower iridium content catalysts (i.e., those containing 0.225 wt.percent lr, for best results, require lesser concentrations ofpalladium. Highly naphthenic feeds permit the use of higher palladiumconcentrations with low iridium to achieve the same degree ofeffectiveness. For paraffinic feeds, low iridium concentrations requirelower palladium concentrations. As the amount of iridium is decreased,the catalyst becomes less tolerant to sulfur contained in the feed,although the sulfurtolerance of the palladium-containing catalysts isgreater than that for the same catalysts without palladium, at allpalladium concentrations within the ranges specified.

The catalyst compositions also contain from about 0.1 to about 2.5percent halogen, preferably from about 0.5 to about 1.5 percent halogen,and from about 0.001 to about 2 percent, and preferably from about 0.001to about 0.1 percent sulfur, based on the total weight (dry basis) ofthe catalyst compositions. Such catalysts, at optimum conditions,possess superior Cf liquid selectivity, even as compared with catalystsotherwise similar which contain equal or greater amounts of iridium, butno palladium. Moreover, the activity of such catalysts, at optimumconditions, surpasses the activity of catalysts otherwise similarexceptthat they contain no palladium, and is not significantly less thancatalysts otherwise similar except that they contain greater amounts ofiridium, but no palladium. [n the preferred combinations at optimumconditions, the activity of the catalyst is compared favorably withconventional platinum-iridium reforming catalysts run at optimumconditions, and when slightly decreased, as with certain feeds at lessthan optimum conditions, this disadvantage is more than offset by theenhanced selectivity, the use of a more available and less expensivemetal, one which is less susceptible to agglomeration, and otherdesirable factors. These platinum-iridiumpalladium catalysts are farmore tolerant to sulfur than catalysts otherwise similar except thatthey contain no palladium, particularly at low iridium levels.

The catalysts of this invention are particularly suitable for use aloneor in admixture with other catalysts, and can be used in one or more ofthe several stages (or reaction zones) of a multiple stage reformingprocess, i.e., one wherein a-series of reactors is provided with beds ofcatalysts, the beds of which are serially contacted with preheated feed.They are particularly effective for the treatment of paraffinic feeds,and quite suitable in reactors following the first reactor of theseries. In a preferred process of this type, fixed beds of the cataiystsare contained in individual reactors (or reaction zones), the naphthafeed is reheated in interstage reheater furnaces to reformingtemperatures and, with hydrogen, is passed sequentially through theseveral reactors of the series. The vapor effluent from the last reactorof the series, a gas rich in hydrogen which usually contains smallamounts of gaseous hydrocarbons, is separated from the C; liquid productand recycled to the process to inhibit coke formation on the catalyst.Hydrogen is produced in net amount in the reaction, which is aparticular advantage in modern refinery operations.

1n the practice of this invention, the metals are composited with mildlyor moderately acidic refractory inorganic oxides which are employed assupports, e.g., silica, silica-alumina, magnesia, thoria, boria,titania, zirconia, various spinels and the like including, inparticular, alumina, and more particularly gamma alumina, which speciesare preferred. High surface area catalysts, or catalysts having surfaceareas ranging upwardly from about M lg. (B.E.T.) are preferred. Inparticular, catalysts having surface areas ranging from about to about600 M /g. prove quite satisfactory.

The platinum, iridium, and palladium components can be composited orintimately associated with the porous inorganic oxide support or carrierby various techniques known to the art such as ion-exchange,coprecipitation with the alumina in the sol or gel form, etc. Forexample, the catalyst composite can be formed by adding togethersuitable reagents such as salts of platinum, iridium, and palladium, andammonium hydroxide or ammonium carbonate, and a salt of alumina such asaluminum chloride or aluminum sulfate to form aluminum hydroxide. Whenthe metals are included in the preparation of the support, higherconcentrations of the metals, particularly of palladium, are oftennecessary. The aluminum hydroxide containing the salts of platinum,iridium, and palladium can then be heated, dried, formed into pellets orextruded, and then calcined in nitrogen or non-agglomerating atmosphere.The palladium is then usually added to the catalyst by impregnation, ifnot previously added, typically via an incipient wetness technique whichrequires a minimum of solution so that the total solution is absorbed,initially or after some evaporation, or by adsorption from dilute orconcentrated solution. The material is then calcined innon-agglomerating atmosphere and then hydrogen treated, or hydrogensulfide treated, or both, in situ or ex situ, to reduce the salts andcomplete the formation of the catalyst composite.

It is generally preferred, however, to deposit all of the metals on thepreviously pilled, pelleted, beaded, extruded, or sieved particulatesupport material by the impregnation method. Pursuant to theimpregnation method, porous refractory inorganic oxides in dry orsolvated state are contacted, either alone or admixed, or otherwiseincorporated with a metal or metalscontaining solution, or solutions,and thereby impregnated by either the incipient wetness technique, or atechnique embodying absorption from a dilute or concentrated solution,or solutions, with subsequent evaporation to effect total uptake ofliquid. The catalyst is then dried and, if smaller particles aredesired, then crushed to form particles of the desired size ranging,e.g., from about 5 to about 200 mesh (Tyler series), and preferablyparticles of about 1/10 to about 1/50 inch average diameter can be used.The support material can be treated by contact with a single solutioncontaining the desired amounts of platinum, iridium, and palladium,which is preferred, or treated sequentially by contact with a solutioncontaining one or more metals, and then a solution which containsanother metal, or metals, in the desired amounts. The catalyst from anypreparative sequence can then be dried, calcined in a non-agglomeratingatmosphere and contacted with hydrogen, or hydrogen sulfide, or both, insitu or ex situ, to reduce part or all of the metal salts and activatethe catalyst.

The incorporation of an acidic or isomerization component within thecatalyst composite is essential. It is preferred to incorporate theacidic or isomerization function required of the catalyst by addition ofhalide, e.g., fluoride, chloride, and the like, particularly chloride,to the catalyst composite to control the rate of isomerization andcracking. This is conveniently and preferably done during the time ofincorporation of the several metals onto the support, or less preferablysubsequent to metals addition to the support. The metals thus can beadded as halide salts of platinum, iridium and palladium duringpreparation of these catalysts. Generally, from about 0.1 to about 2.5weight percent, and preferably from about 0.5 to about 1.5 percent,based on the weight of the total catalyst composite, of the halide isadded during manufacture of the catalyst, though halogen can also beadded, or replenished, during regeneration or in situ during normalreforming operations. A platinum-iridium-palladium catalyst containingfrom about 0.5 to about 1.2 percent halogen, particularly chlorine, hasbeen found to provide superior selectively, while yet substantiallyretaining the activity of the platinum-iridium catalyst. Moreover, theactivity can be retained even when the iridium concentration of thecatalyst containing the triumvirate of metals is reduced tosubstantially one-half that which is present in the usual bimetalliccomposition.

The partially dried catalyst, after incorporation of the metals, andhalogen, is then completely dried or calcined in nitrogen or othernon-agglomerating medium, either in situ or ex situ, as related to thereactor in which the naphtha reforming reaction is to be carried out.The general method is to carry out the drying in flowing nitrogen whileraising the temperature stepwise to avoid too high a concentration ofwater vapor. The temperature is generally increased to 800-] ,000F. andthe gas flow maintained until the catalyst is essentially completelydry. It is very important that the catalyst be essentially dry before itis reduced or contacted with hydrogen in order to avoid metalsagglomeration. The catalyst is then reduced, generally with hydrogen ora hydrogen-containing gas, the platinum and iridium being reducedsubstantially to the metallic state before the catalyst is subjected toreforming conditions. The reduction is generally carried out by passingthe hydrogen through the zone of contact with the catalyst at sufficientvelocity to rapidly sweep out the water vapor that is formed. Thetemperature of reduction is not especially critical, but is generallycarried out in the range of about 500 to about 1,000F. The time requiredfor reduction of the noble metals is generally short and not more thanan hour, or at least no more than one to four hours, is generallyrequired to complete the reduction.

Following the reduction, the catalyst is sulfided by contact with asulfide, generally hydrogen sulfide or compound which will producehydrogen sulfide in situ. The contact of a hydrogen sulfide-containinggas with the catalyst serves a number of functions, and has a profoundinfluence on the reforming performance of the catalyst. In sulfiding thecatalyst, the catalyst is contacted with a dilute gaseous solution,e.g., about 50 to about 5,000 ppm, preferably about 1,000 to about 3,000ppm, of hydrogen sulfide in hydrogen, or hydrogen plus other nonreactivegases. The contacting of the catalyst with this gas is conducted atabout 500 to about 1,000F., preferably from about 700F. to about 950F.,and is continued until hydrogen sulfide is detected in the effluent gas.Such treatment incorporates from about 0.001 to about 2 weight percent,and preferably from about 0.01 to about 0.1 weight percent sulfur on thecatalyst.

Essentially any hydrocarbon fraction containing paraffins, naphthenes,and the like, admixed one with the other or in admixture with otherhydrocarbons, can be converted by means of the catalysts of thisinvention. A suitable feed, e.g., either virgin or cracked, Fischer-Tropsch or mixtures thereof, is contacted at reforming conditions in thepresence of hydrogen (once-through, or recycle) with a catalystcomposite including a support which contains catalytically activeamounts of the metals. Typical feed stream hydrocarbon molecules arethose containing from about 5 to about 12 carbon atoms, or morepreferably from about 6 to about 12 carbon atoms, or more preferablyfrom about 7 to about 10 carbon atoms. Naphthas, or petroleum fractions,boiling within the range of from about F. to about 450F., and preferablyfrom about l25F. to about 375F., contain hydrocarbons or carbon numberswithin these ranges. Typical fractions thus usually contain from about20 to about 80 volume percent of paraffins, both normal and branched,which fall in the range of about C to C 2, and from about to about 80volume percent of naphthenes boiling within the range of about C to CTypical feeds generally contain from about 5 through about 20 volumepercent of aromatics which boil within the range of about C to Ctypically as produced in the product from the naphthenes and paraffins.

It is essential, for best results, that the feed contain a small amountof sulfur. Preferably, the feed shall contain from about 0.05 to about15 parts, per million parts of feed (ppm), and more preferably fromabout 0.2 to about 2.0 ppm of sulfur.

The reforming reaction is suitably conducted at temperatures rangingfrom about 600 to about 1050F., and preferably at temperatures rangingfrom about 850 to about 1,000F. Pressures range generally from about 50to about 750 psig, and preferably from about 100 to about 500 psig. Thereactions are conducted in the presence of hydrogen to suppress sidereactions normally leading to the formation of unsaturated carbonaceousresidues, or coke, which deposits upon and causes deactivation of thecatalyst. The hydrogen rate, once-through or recycle, is generallywithin the range of from about 1,000 to about 10,000 SCF/Bbl, andpreferably within the range of from about 2,000 to about 5,000 SCF/Bbl.The feed stream, in admixture with hydrogen, is passed over beds of thecatalyst at space velocities ranging from about 0.1 to about W/W/Hr.,and preferably from about 0.5 to about 5.0 W/W/Hr.

The invention will be more fully understood by reference to thefollowing selected nonlimiting examples and comparative data whichillustrate its more salient features. All parts are given in terms ofweight except as otherwise specified.

Several catalysts were prepared for demonstrative purposes from portionsof particulate alumina of the type conventionally used in themanufacture of commercial reforming catalysts. The portions of aluminawere impregnated with a solution of salts of the metals to be compositedtherewith, treated and activated and then employed as catalysts in aseries of representative reforming reactions. The portions of alumina,except in the instance wherein bimetallic platinum-iridium catalysts(Catalysts A and B), and platinum catalyst (Catalyst C), all of whichwere prepared and employed as controls for comparative purpose, wereimpregnated with aqueous acid solutions containing a mixture ofplatinum, iridium, and palladium salts (Catalysts D, E, and F). Theplatinum-iridium catalysts (Catalysts A and B) were similarly preparedexcept that the palladium salt was not added to the solution and, asregards the platinum catalyst (Catalyst C), both the iridium andpalladium salts were eliminated from the solution.

These series of catalysts were each evaluated in a continuously operatedreactor for reforming naphtha at essentially the same conditions oftemperature, pressure and hydrogen rate. The space velocity of theseveral reactions was varied, as identified in the tabulated data. Thedata related to catalyst preparation, and naphtha reforming, are givenbelow, the data on catalyst preparations being given in the examples anddemonstrations immediately following:

EXAMPLES CATALYST PREPARATIONS Catalyst A (Platinum-High Iridium) Aportion of high purity gamma alumina extrudates, previously calcined,was crushed and screened to 14-35 mesh (Tyler), then calcined about 2hours in a flow of air or nitrogen at 1000F. The calcined alumina (50.00gms) was impregnated with a solution prepared by mixing 6.00 cc. Ptstocksolution (25.0 mg. Pt/ml and 27.3 mg. Cl/cc.) and 7.74 cc. 1r stocksolution 19.4 mg. lr/ml, 25.5 mg. Cl/cc.) and diluted to approximately65 ml with deionized water. After allowing the solution to stand for aperiod of one hour, by which time the remaining solution, if any, wascolorless, the catalyst was dried in the vacuum oven to about 400F. Thecatalyst was then charged to a resistance heated Vycor tube and heatedat 9501,000F. in a flow of nitrogen for 3 hours and was then reduced inhydrogen at 9009l0F. for 2 hours. The catalyst was then sulfided bytreatment with a flowing hydrogen-14 mixture (0.3 percent H 5) which wasfurther diluted with hydrogen and nitrogen. This was done at 900-9l0F.until H S broke through the bottom of the bed and was detected withmoist lead acetate paper.

The composition of this Catalyst A is as follows:

Pt, 0.29%; Ir, 032%; Cl, 0.65%; S, 0.10%. Catalyst B (Platinum-LowIridium) A previously calcined portion of gamma alumina particles wascalcined, again as in the preparation of Catalyst A. The portion ofalumina (50.00 gm) was then impregnated with a solution similar to thatused in the preparation of Catalyst A except that it contained onehalfas much of the iridium stock solution, and 1.81 milliliters of anaqueous solution which contaiined 48.6 mg of chloride/ml as HCl. Afterimpregnation, the catalyst was dried, calcined, reduced and sulfided asin the preparation of Catalyst A.

The catalyst composition is as follows:

Pt, 0.30%; Ir, 0.16%; Cl, 0.67%; S, 0.14%.

Catalyst C (Platinum) Another portion of previously calcined gammaalumina of 14-35 mesh particle size was calcined as in the preparationof Catalysts A and B. Alumina (50.00 g) was impregnated with a solutioncontaining 6.00 ml chloroplatinic acid solution containing 25.0 mgPt/ml, and 27.3 mg Cl/ml and 2.80 milliliters of an aqueous solutionwhich contained 48.6 mg of chloride/ml as HCl diluted to about 65 mlwith deionized water. The platinum-alumina precatalyst was dried,calcined and reduced as described in the procedure for Catalyst A. Thiscatalyst was not sulfided as were the iridium catalysts.

The composition of the catalyst is as follows:

Pt, 0.29%; Cl, 0.60%.

Catalyst D (Platinum-Iridium-Palladium) Again, a previously calcinedportion of gamma alumina particles was further calcined as in thepreparation of Catalyst A. The alumina (50.00 g) was impregnated with asolution containing 6.00 ml of chloroplatinic acid stock solutioncontaining 25.0 mg Pt/ml, and 27.3 mg Cl/ml, 7.74 ml of chloroiridicacid stock solution containing 19.4 mg lr/ml and 25.5 mg Cl/ml, 0.30

ml of a chloropalladous acid stock solution containing 24.0 mg Cllml and26.8 mg Cl/ml, and 1.64 ml of a hydrochloric acid stock solutioncontaining 48.6 mg Cl/ml, all diluted to about 65 ml with deionizedwater. After impregnation, the catalyst was dried, calcined, reduced andsulfided as in the preparation of Catalysts A and B. l

The composition of the catalystsis given as follow:

Pt, 0.31%; lr, 0.16%; Cl, 0.68%; Pd, 0.008%; S, 0.16%.

Catalyst E (Platinum-Iridium-Palladium) Particulate gamma alumina of14-35 mesh particle size was calcined, again as in the preparation ofCatalyst A. The alumina (50.00 g) was impregnated with a solutionsimilar to that used for Catalyst D except that it contained anadditional 0.30 ml of the solution of chloropall'adous acid stocksolution'and the quantity of hydrochloric acid solution used was reducedto 1.32 ml. After impregnation, the catalyst was dried, calcined,reduced and sulfided as in the preparation of Catalyst A, B, and D.

The composition of the catalyst is as follows:

Pt, 0.31%; It, 0.15%; Cl, 0.67%; Pd, 0.025%; S, 0.11%. Catalyst F(Platinum-1ridium-Pa11adium) A portion of previously calcined gammaalumina of 14-35 mesh particle size was again calcined as in thepreparation of Catalyst A. The alumina (50.00 g) was impregnated with asolution similar to that used for Catalyst D except that it contained anadditional 1.26 ml of the stock solution of chloropalladous acid and thequantity of the hydrochloric acid stock solution used was reduced to0.93 ml. After impregnation, the catalyst was dried, calcined, reducedand sulfided as in the preparation of Catalysts A, B, D, and E.

The composition of the catalyst is as follows:

Pt, 0.31%; Ir, 0.16%; CI, 0.82%; Pd, 0.09%; S, 0.15%.

REFORMING RUNS These several catalysts, after their preparation, wereallowed to cool under nitrogen at low flow rate, handled under nitrogen,and stored under nitrogen and/or purified and dried hydrocarbon,generally normal heptane. Each was subsequently evaluated in extendedreforming tests in a small continuous flow, once-through, or non-cyclic,reactor with a typical highly paraffmic Aramco feed and a typical, morenaphthenic Baytown virgin naphtha feed, respectively. The inspections oneach of the feeds are .presented in Table 1 as follows:

TABLE l-Continued A series of reforming runs, as shown by reference toTables 2 through 6, were conducted with each of these several catalysts,Catalysts A, B and C being employed as referencesfor determination ofthe effectiveness of the novel catalysts of this invention which employthe triumvirate of metals, viz., platinum, iridium and palladium(Catalysts D, E and F). Catalysts A and B, the high iridium and lowiridium catalysts, respectively, were employed to reform each of the twofeeds, respectively, to each of which was added 1.0 ppm of sulfur, thisconcentration of sulfur being about optimum for the high iridiumcatalyst. The platinum only catalyst (Catalyst C) was used to reform theAramco feed at generally optimum conditions, the feed containing noadded sulfur. Catalyst D, which contained an optimum concentration ofpalladium, as shown by reference to Tables 7 through 9, was employed toreform each of the two feeds, the Aramco Naphtha at different sulfurlevels, viz., at 1.0 ppm of sulfur and at 0.4 ppm of sulfur, and theBaytown Naphtha at 0.4 ppm of sulfur, to obtain comparisons between theactivity and selectivity of Catalysts A, B and C employed as standardsat the generally optimum conditions of each. Results of tests conductedon Catalysts E and F, containing higher concentrations of palladium, ononly one feed at two sulfur levels are given in Tables 10, 1 1 and 12for comparison with Catalyst D, containing an optimum level ofpalladium.

Each of the reforming tests was conducted at conditions, inclusive ofthe following:

Sandbath Temperature, "F 925 (lsothennal) (920F., E.1.T.) 200 Pressure,Psi Hydrogen Recycle Rate, SCF/B TABLE 2 CATALYST A 0.29% Pt; 0.32% Ir;0.65% C1 Run Conditions: Aramco Naphtha at 1.0 ppm S 1.0 Wll-lrJW SpaceVelocity C Product Aromatics in Hours on Feed Yield C Product Calculated(End of Balance) (Volume (Volume RON TABLE 2-Continued Run Conditions:

C Product Aromatics in Hours on Feed Yield C Product Calculated (End ofBalance) (Volume (Volume RON TABLE 3 CATALYST A Run Conditions: AramcoNaphtha at 1.0 ppm S 2.6 W/Hr./W Space Velocity (2 Product Aromatics inHours on Feed Yield C Product Calculated (End of Balance) (Volume(Volume RON TABLE 4 CATALYST A Run Conditions:

Baytown Virgin Naphtha at 1.0 ppm S 2.7 W/HrJW Space Velocity Cf ProductAromatics in CATALYST A Run Conditions:

TABLE 4-Continued 2.7 W/HrJW Space Velocity C Product Aromatics in Hourson Feed Yield C, Product Calculated (End of Balance) (Volume (Volume RON290.5 I I 80.1 I 66.2 100.5 307.5 1 79.7 66.5 100.6 314.5 80.3 66.0100.4 331.5 79.4 66.8 100.7 338.5 80.8 66.3 100.5 355.5 80.5 66.2 100.5362.5 79.0 v 67.3 100.9 379.5 80.1 66.2 100.5 386.5 78.1 67.1 100.9458.5 79.9 66.5 100.6 .475.5 80.7 66.8 100.7 482.5 80.3 64.5 99.8

TABLE 5 v CATALYST B 0.30% Pt; 0.16% 1r; 0.67% Cl Run Conditions: AramcoNaphtha at 1.0 ppm S 1.1 W/HrJW Space Velocity C; Product Aromatics inHours on Feed Yield C; Product Calculated (End of Balance) (Volume(Volume RON TABLE 6 CATALYST C 0.29% Pt; 0.60% Cl Run Conditions: AramcoNaphtha at 0.0 ppm S 1.1 W/HrJW Space Velocity a C; Product Aromatics inHours on Feed Yield C Product Calculated (End of Balance) (Volume(Volume RON TABLE 7 CATALYST D-- 0.31% Pt; 0.16% 1r; 0.008% Pd; 0.68%CI.

' Aramco Naphtha at 1.0 ppm S Run Conditions:

TABLE 8 CATALYST D Run Conditions:

C Product Aromatics in Hours on Feed Yield C Product Calculated (End ofBalance) (Volume (Volume RON TABLE 9 CATALYST D Run Conditions:

Baytown Virgin Naphtha at 0.4 ppm S 2.7 W/Hr./W Space Velocity C ProductAromatics in CATALYST E 0.31% Pt; 0.15% Ir; 0.025% Pd; 0.67% CI AramcoNaphtha at 1.0 ppm S 1.1 W/HrJW Space Velocity Run Conditions:

C Product Aromatics in Hours on Feed Yield C; Product Calculated (End ofBalance) (Volume (Volume RON TABLE 1 1 CATALYST E Run Conditions: AramcoNaphtha at 0.4 ppm S 1.0 W/HrJW Space Velocity CJ Product Aromatics inHours on Feed Yield C Product Calculated (End of Balance) (Volume(Volume RON TABLE 12 CATALYST F 0.31% Pt; 0.16% lr; 0.09% Pd; 0.82% CIRun Conditions: Aramco Naphtha at 1.0 ppm S 5 1.0 W/HL/W Space VelocityC; Product Aromatics in Hours on Feed Yield C Product Calculated (End ofBalance) Volume (Volume RON The more important aspects of these data aregraphically illustrated, for convenience, by reference to the attachedFIGURE. 1n the FIGURE, the data obtained for the series of runsemploying Catalysts A, B, C and D are plotted in terms of C ProductYield (volume percent), which is a measure of the selectivity of thecatalysts, and the Aromatics Concentration (volume percent) of the C;Product, which is a measure of the activity of the catalysts. The CProduct Yield (volume percent) is plotted on the vertical axis and theAromatics Concentration (volume percent) is plotted on the horizontalaxis of the graph. Additionally, the approximate Research Octane Number(RON), calculated on the basis of aromatics concentration, is plotted onthe horizontal axis of the graph.

For purposes of comparison, the FIGURE depicts graphical data relatingto a large number of runs made with Catalysts A, B and C of which thedata given in Tables 2 through 6 are typical, and data plotted from runsmade with Catalyst D. The activity-selectivity curve for Catalyst A,presented graphically in the FIGURE, is thus inclusive of the two runsfor which data are listed in Tables 2 and 3, these data being typical ofa larger group of runs from which the entire activity-selectivity curvefor Catalyst A is taken and employed as a standard for the 1.0 ppm sufurAramco feed runs. The solid unbroken line in the FIGURE thus illustratesa standard to which other data may be compared in a manner which is moreeasily understood than tabular data. Likewise, the dashed line in theFIGURE was drawn from a larger set of data of which the data in Table 4are typical, again for Catalyst A, but in this case for Baytown virginnaphtha utilizing 1.0 ppm sulfur. The elipses depicted in the FIGURErepresents areas in which a collection of data points occur. The solidellipse for Aramco feed and the dashed ellipse for the Baytown feedrepresent, respectively, the areas in which the lined-out activity ofCatalyst A occurs as illustrated in the data presented by Tables 2 and4, respectively. Lined-out activity means a relatively constant activityand selectivity which occurs after the initial period of an operatingrun when the activity significantly decreases and becomes relativelystable. The dashed-dot ellipse of the FIGURE represents an area in whichthe data for the lined-out activity of Catalyst B occurs, the datatabulated in Table 5 being illustrative. The dotted line depicted in theFIGURE represents a collection of data of which the run on Catalyst C astabulated in Table 6 is illustrative. In the case of this type ofcatalyst, there is typically no lined-out activity. The catalystdeactivates and data on any single run moves 1 from right to left alongthe dotted line (within the range of experimental error).

In the FIGURE, there is thus presented a summary of data, the lines andellipses made with each of Catalysts A and B for both the Aramco andBaytown virgin naphtha feeds, each containing sulfur at the 1.0 ppmlevel.

Runs conducted with Catalyst C, also depicted on the graph, wereconducted only with the Aramco feed which contained no sulfur. The runsconducted by reforming the Aramco feed are presented in the FIGURE bythe graphical data presented at the lower portion of the sheet, andthose conducted by reforming the Baytown virgin naphtha feed at theupper portion of the sheet. Runs conducted with Catalyst A on theBaytown virgin naphtha feed are depicted (at the upper portion of thesheet) in the FIGURE by a broken or dashed black line, and the lined-outactivity of the catalyst is depicted by the dashed line ellipse withinwhich would lie a collection of points representative of the lined-outactivity of the catalyst.

Runs made with Catalyst D on both the Aramco feed and the Baytown virginnaphtha feeds at sulfur levels of 0.4 ppm are plotted as clusters ofpoints on the FIG- URE, and one run with Catalyst D made on the Aramconaphtha feed at a sulfur level of 1.0 ppm is plotted as a cluster ofpoints on the FIGURE. In contrasting these data with the data presentedfor Catalysts A, B and C, a number of observations are apparentconcerning the effectiveness of platinum-iridiumpalladium catalysts, asrepresented by Catalyst D vis-avis platinum and platinum-iridiumcatalysts generally.

Referring to the FIGURE, it will be observed that in treating the Aramcofeed at the 1 ppm sulfur level, the platinum-iridium-palladium catalyst(Catalyst D) is only slightly lower in activity than theplatinum-iridium catalyst (Catalyst A), albeit the former contains onlyabout one-half as much iridium. On the other hand, Catalyst D hassuperior selectivity, providing 3-5 percent better C Product Yield atconstant octane. Thus, for a decrease of about l-2 RON, a selectivityadvantage of 3-5 percent is gained, and only about one-half as muchiridium is used in preparation of the catalyst.

A catalyst similar in composition to Catalyst D, except that it containsno palladium, but only platinum and iridium in equal concentration,i.e., Catalyst B, is a poorer catalyst. The lined-out activity ofCatalyst B thus produces a C; product about 2 RON below that of CatalystD at the same conditions of operation. The selectivity of Catalyst D atlower octane number levels is also generally better than that ofCatalysts A and B at the same octane levels.

Again referring to the FIGURE, it will be observed that in treating theAramco feed at the 0.4 ppm sulfur level, that Catalyst D has about thesame activity as at its optimum sulfur level of 1.0 ppm, but it showsless selectivity advantage than at its optimum which ranges 2-3 percentless than at the 1.0 ppm sufur level. Nevertheless, there is a 1-2percent yield advantage for Catalyst D at a 0.4 ppm sulfur level ascompared with Catalyst A at its optimum conditions. When Catalyst D iscompared with Catalyst A, again as shown in the FIG- URE wherein dataregarding the performance of these catalysts is depicted as inprocessing Baytown naphtha feed, each at its optimum sulfur level, it isseen that Catalyst D provides a /2 to 1 percent yield advantage, atgiven RON level, over Catalyst A. Catalyst D, on the other hand,possesses about the same activity as a catalyst which contains abouttwice as much iridium, but no palladium. Thus, even though theadvantages of the platinum-iridium-palladium catalysts are not sharplydistinguished as with the more difficult paraffinic feeds, theadvantages are. nonetheless present. Moreover, since the optimum sulfurlevelin processing the Aramco feed is 1.0 ppm, it is also apparent thatbetter selectivity would occur at the 1.0 ppm sulfur. level vis-avis the0.4-ppm sulfur level in processing-the Baytown virgin naphtha feed.

In the runs conducted with Catalysts A and D which utilized Baytownvirgin naphtha feed containing 0.4 ppm sulfur, it is apparent thatCatalyst D possesses a selectivity advantage over Catalyst A. Thus, at agiven octane level, Catalyst D, at optimum conditions, provides from l-2percent Cf Product yield advantage.

From these series of data, it is apparent that the incorporation ofpalladium with platinum-iridium catalysts makes these catalysts muchmore sulfur-tolerant. The substitution of palladium for iridium actuallyproduces a superior catalyst. In other words, platinum-iridium-palladiumcatalysts are superior to platinum-iridium catalysts when thesedifferent catalysts are each operated at their optimum conditions. Infact, as illustrated by the data, even though Catalyst D operatedeffectively at the 0.4 ppm sulfur level, and provided advantages overits bimetallic counterpart, its performance is even better at the 1.0ppm sulfur level where Catalyst A operates at its optimum. Anotheradvantage is that the use of large amounts of palladium in thesecatalysts is unnecessary, the smaller amounts of palladium being moreeffective than the larger concentrations. For example, Catalyst D, whichcontains about one-half as much palladium as Catalyst E, shows superioractivity and selectivity as contrasted with the latter. This is shown atboth sulfur levels by comparison of Tables 7 and 10, and 8 and 1 1.Likewise, Catalyst F shows poorer activity and selectivity than CatalystD, as shown by comparisons between Tables 7 and 12. Comparing CatalystsE and F (Tables l0, l1 and 1 2) with Catalyst B (Table 5),-similar tothe former catalystsbut containing no palladium, it becomes apparentthat both palladium-containing catalysts exhibit no significant activityadvantage but show a selectivity advantage amounting to about /-lpercent yield at any given octane. All palladium levels appearto'provide selectivity advantages over the same catalyst, without thepalladium. The low level of palladium, however, provides both activityand selectivity as contrasted with high palladium or with similarcatalysts containing no palladium. H

It is essential that the catalyst composition of this invention containthe triumvirate of metals--viz., platinum, iridium andpalladium,deposited or otherwise incorporated, preferably impregnated, upon aporous inorganic oxide base in catalytically active concentrations. Thecatalytically active metals can be present, e.g., as metallic metal, oras oxides, chlorides,-oxychlorides, aluminates, carbides, hydrides, orsulfides of the metal, or as mixtures thereof with these and, other lessdescribable structures. Under the varying conditions of forming andusing the catalysts, it is likely that the metals will vary in theiractual distribution as oxides, chlorides, oxychlorides, aluminates,carbides, hydrides, sulfides, or reduced forms of the metals, ormixtures thereof with these and other less describable structures. Themetals, however, are calculated o n th e basis of metallic metal. Thecatalytically active metals are composited with the porous inorganicoxide bases by methods known to the .art. Preferably, the metals aresimultaneously impregnated on the support and, after impregnation of thesupport by contact with an acid solution, or solutions, of salts ofthemetals, the so formed composite is dried atconditions rangingfrom about200 to about 400F., often at reduced pressure or in'a stream of flowinggas, then; further dried and calcined attemperatures ranging up to about1200F. in an atmosphere which does not agglomerate the iridium or othermetals. The catalyst then may be contacted in situ or ex situ withhalogen, halogen precursor, halide or halide precursor. Halogen,preferably chlorine, and next in preference fluorine, is generally addedat the time of catalyst preparation as the acid in the metalsimpregnation solution. Additional halogen can be added during reformingoperations to maintain desired operating levels. The catalyst is thensulfided, generally by contact with P1 8 in dilute gaseous mixture toconvert at least some of the metals to the corresponding sulfides. Aswith the halides, the feeds can be spiked with sulfur compounds, orother higher sulfur feed, to add sulfide to the catalyst duringoperation. H S, l'lCl, or other gases containing sulfur or halogen canalso be added to the recycle gas streams to change catalyst sulfurhalide levels during operation.

It is apparent that various modifications and changes can be madewithout departing the spirit and scope of the present invention, anoutstanding feature of which is that the octane quality of varioushydrocarbon feedstocks, inclusive particularly of paraffinic feedstocks,can be upgraded and improved.

Having described the invention, what is claimed is:

1. A catalyst suitable for conversion of hydrocarbons comprising acomposite of an acidic porous inorganic oxide support, platinum inconcentration ranging from about 0.05 to about 3 percent, iridium inconcentration ranging from about 0.05 to about 3 percent, palladium inconcentration ranging from about 0.0001 to about 2.5 percent, andhalogen in concentration ranging from about 0.1 to about 2.5 percentbased on the total weight of the catalyst, the atom ratio of theplatinum- :iridium ranging from about 0.25:1 to about 5:1, and the atomratio of iridiumzpalladium ranging from about 1:1 to about 40:1.

2. The catalyst of claim 1 wherein the composite comprises from about0.1 to about 1.0 percent platinum, from about 0.1 to about 1.0 percentiridium, and from about 0.0005 to about 0.15 percent palladium.

3. The catalyst of claim 2 wherein the palladium ranges from about0.0050 to about 0.050 percent.

4. The catalyst of claim 1 wherein the halogen is chlorine.

5. The catalyst of claim 1 wherein the composite contains from about 0.5to about 1.5 percent halogen.

6. The catalyst of claim 1 wherein the porous inorganic oxide support isalumina.

7. The catalyst of claim 1 wherein the composite contains from about0.001 to about 2 percent sulfur.

8. The catalyst of claim 1 wherein the composite contains from about0.01 to about 0.1 percent sulfur.

9. The catalyst of claim 1 wherein the atom ratio of iridiumzpalladiumranges from about 2:1 to about 1.

10. The catalyst of claim 1 wherein the atom ratio of theplatinum:iridium ranges from about 1:1 to about 18 2: 1, and the atomratio of the iridiumzpalladium ranges from about 2:1 to about 10:1. 11.The catalyst of claim 2 wherein the atom ratio of the platinum:iridiumranges from about 1:1 to about alumina, platinum in concentrationranging from about 0.05' to about 1 percent, iridium in concentrationranging from about 0.05 to about 1 percent, palladium in concentrationranging from about 0.0001 to about 2.5 percent, chlorine inconcentration ranging from about 0.5 to about 1.5 percent, and sulfur inconcentration ranging from about 0.001 to about 2 percent, the atomratio of the platinum:iridium ranging from about 0.25:1 to about 5:1,and the atom ratio of iridium:palladium ranging from about 1:1 to about40: 1.

14. The composition of claim 13 wherein the palladium ranges from about0.0050 to about 0.050 percent.

15. The catalyst of claim 13 wherein the alumina is gamma alumina, andthe sum total concentration of the platinum and iridium ranges fromabout 0.3 to about 1 percent.

16. The catalyst of claim 13 wherein the sum total amount of platinumand iridium ranges from about 0.3 to about 1 percent, and the atom ratioof the iridium:- palladium ranges from about 1:1 to about 40:1.

17. The catalyst of claim 13 wherein the sum total amount of platinumand iridium ranges from about 0.45 to about 0.70 percent, and the atomratio of the iridium2palladium ranges from about 2:1 to about 10: 1.

18. The catalyst of claim 13 wherein the atom ratio of theplatinum:iridium ranges from about 1:1 to about 2:1, and the atom ratioof iridiumzpalladium ranges from about 2:1 to about 10:1.

19. The catalyst of claim 13 wherein the concentration of the palladiumranges from about 0.0005 to about 0.15 percent.

20. The catalyst of claim 19 wherein the atom ratio of theplatinum:iridium ranges from about 1:1 to about 2:1, and the atom ratioof iridiumzpalladium ranges from about 2:1 to about 10:1.

21. A process for improving the octane quality of naphthas comprisingcontacting the said naphtha at reforming conditions with a compositecomprising a porous inorganic oxide support, platinum in concentrationranging from about 0.05 to about 3 percent, iridium in concentrationranging from about 0.05 to about 3 percent, palladium in concentrationranging from about 0.0001 to about 2.5 percent, and halogen inconcentration ranging from 0.1 to about 2.5 percent based on the totalweight of the catalyst, the atom ratio of the platinum:iridium rangingfrom about 0.25:1 to about 5:1, and the atom ratio of iridiumzpalladiumranging from about 10:1 to about 40:1.

22. The process of claim 21 wherein the palladium ranges from about0.0005 to about 0.15 percent.

23. The process of claim 21 wherein the palladium ranges from about0.0050 to about 0.050 percent.

24. The process of claim 21 wherein the catalyst composite comprisesfrom about 0.1 to about 1.0 percent platinum, from about 0.1 to about1.0 percent irid- 19 ium and from about 0.0005 to about 0.15 percentpalladium.

25. The process of claim 24 wherein the sum total concentration ofplatinum and iridium ranges from about 0.3 to about 1 percent.

26. The process of claim 21 wherein the composite comprises from about0.5 to about 1.5 percenthalogen.

27. The process of claim 26 wherein the halogen is chlorine.

28. The process of claim 21 wherein the porous inorganic oxide supportis alumina.

29. The process of claim 21 wherein the catalyst contains from about0.001 to about 2 percent sulfur.

30. The process of claim 29 wherein the catalyst contains from about0.01 to about 0.1 percent sulfur.

31. The process of claim 21 wherein reforming is 20 conducted attemperatures ranging from about 600F. to about 1,050F., at pressuresranging from about 50 psig to about 750 psig, at space velocitiesranging from about 0.1 to about 25 W/Hr./W, and at hydrogen ratesranging from about 1000 to about 10,000 SCF/Bbl.

32. The process of claim 31 wherein temperatures ,range from about 850F.to about 1,000F., pressures from about 2:1 to about 10:1.

l I i i

1. A CATALYST SUITABLE FOR CONVERSION OF HYDROCARBONS COMPRISING ACOMPOSITE OF AN ACIDIC POROUS INORGANIC OXIDE SUPPORT, PLATINU, INCONCENTRATION RANGING FROM ABOUT 0.05 TO ABOUT 3 PERCENT, IRIDIUM INCONCENTRATION RANGING FROM ABOUT 0.05 TO ABOUT 3 PERCENT, PALLADIUM INCONCENTRATION RANGING FROM ABOUT 0.0001 TO ABOUT 2.5 PERCENT, ANDHALOGEN IN CONCENTRATION RANGING FROM ABOUT 0.1 TO ABOUT 2.5 PERCENTBASED ON THE TOTAL WEIGHT OF THE CATALYST, THE ATOM RATIO OF THEPLATINUM:IRIDIUM RANGING FROM ABOUT 0.25:1 TO ABOUT 5:1, AND THE ATOMRATIO OF IRIDIUM:PALLADIUM RANGING FROM ABOUT 1:1 TO ABOUT 40:1.
 2. Thecatalyst of claim 1 wherein the composite comprises from about 0.1 toabout 1.0 percent platinum, from about 0.1 to about 1.0 percent iridium,and from about 0.0005 to about 0.15 percent palladium.
 3. The catalystof claim 2 wherein the palladium ranges from about 0.0050 to about 0.050percent.
 4. The catalyst of claim 1 wherein the halogen is chlorine. 5.The catalyst of claim 1 wherein the composite contains from about 0.5 toabout 1.5 percent halogen.
 6. The catalyst of claim 1 wherein the porousinorganic oxide support is alumina.
 7. The catalyst of claim 1 whereinthe composite contains from about 0.001 to about 2 percent sulfur. 8.The catalyst of claim 1 wherein the composite contains from about 0.01to about 0.1 percent sulfur.
 9. The catalyst of claim 1 wherein the atomratio of iridium: palladium ranges from about 2:1 to about 10:1.
 10. Thecatalyst of claim 1 wherein the atom ratio of the platinum:iridiumranges from about 1:1 to about 2:1, and the atom ratio of theiridium:palladium ranges from about 2:1 to about 10:
 11. The catalyst ofclaim 2 wherein the atom ratio of the platinum:iridium ranges from about1:1 to about 2:1, and the atom ratio of the iridium:palladium rangesfrom about 2:1 to about 10:
 12. The catalyst of claim 3 wherein the atomratio of the platinum:iridium ranges from about 1:1 to about 2:1, andthe atom ratio of the iridium:palladium ranges from about 2:1 to about10:
 13. A reforming catalyst comprising a composite of alumina, platinumin concentration ranging from about 0.05 to about 1 percent, iridium inconcentration ranging from about 0.05 to about 1 percent, palladium inconcentration ranging from about 0.0001 to about 2.5 percent, chlorinein concentration ranging from about 0.5 to about 1.5 percent, and sulfurin concentration ranging from about 0.001 to about 2 percent, the atomratio of the platinum:iridium ranging from about 0.25:1 to about 5:1,and the atom ratio of iridium:palladium ranging from about 1:1 to about40:1.
 14. The composition of claim 13 wherein the palladium ranges fromabout 0.0050 to about 0.050 percent.
 15. The catalyst of claim 13wherein the alumina is gamma alumina, and the sum total concentration ofthe platinum and iridium ranges from about 0.3 to about 1 percent. 16.The catalyst of claim 13 wherein the sum total amount of platinum andiridium ranges from about 0.3 to about 1 percent, and the atom ratio ofthe iridium:palladium ranges from about 1:1 to about 40:1.
 17. Thecatalyst of claim 13 wherein the sum total amount of platinum andiridium ranges from about 0.45 to about 0.70 percent, and the atom ratioof the iridium:palladium ranges from about 2:1 to about 10:1.
 18. Thecatalyst of claim 13 wherein the atom ratio of the platinum:iridiumranges from about 1:1 to about 2:1, and the atom ratIo ofiridium:palladium ranges from about 2:1 to about 10:1.
 19. The catalystof claim 13 wherein the concentration of the palladium ranges from about0.0005 to about 0.15 percent.
 20. The catalyst of claim 19 wherein theatom ratio of the platinum:iridium ranges from about 1:1 to about 2:1,and the atom ratio of iridium:palladium ranges from about 2:1 to about10:1.
 21. A process for improving the octane quality of naphthascomprising contacting the said naphtha at reforming conditions with acomposite comprising a porous inorganic oxide support, platinum inconcentration ranging from about 0.05 to about 3 percent, iridium inconcentration ranging from about 0.05 to about 3 percent, palladium inconcentration ranging from about 0.0001 to about 2.5 percent, andhalogen in concentration ranging from 0.1 to about 2.5 percent based onthe total weight of the catalyst, the atom ratio of the platinum:iridiumranging from about 0.25:1 to about 5:1, and the atom ratio of iridium:palladium ranging from about 10:1 to about 40:1.
 22. The process ofclaim 21 wherein the palladium ranges from about 0.0005 to about 0.15percent.
 23. The process of claim 21 wherein the palladium ranges fromabout 0.0050 to about 0.050 percent.
 24. The process of claim 21 whereinthe catalyst composite comprises from about 0.1 to about 1.0 percentplatinum, from about 0.1 to about 1.0 percent iridium and from about0.0005 to about 0.15 percent palladium.
 25. The process of claim 24wherein the sum total concentration of platinum and iridium ranges fromabout 0.3 to about 1 percent.
 26. The process of claim 21 wherein thecomposite comprises from about 0.5 to about 1.5 percent halogen.
 27. Theprocess of claim 26 wherein the halogen is chlorine.
 28. The process ofclaim 21 wherein the porous inorganic oxide support is alumina.
 29. Theprocess of claim 21 wherein the catalyst contains from about 0.001 toabout 2 percent sulfur.
 30. The process of claim 29 wherein the catalystcontains from about 0.01 to about 0.1 percent sulfur.
 31. The process ofclaim 21 wherein reforming is conducted at temperatures ranging fromabout 600*F. to about 1,050*F., at pressures ranging from about 50 psigto about 750 psig, at space velocities ranging from about 0.1 to about25 W/Hr./W, and at hydrogen rates ranging from about 1000 to about10,000 SCF/Bbl.
 32. The process of claim 31 wherein temperatures rangefrom about 850*F. to about 1,000*F., pressures range from about 100 psigto about 250 psig, space velocities range from about 1.0 to about 5.0W/W/Hr., and the hydrogen rate ranges from about 2,000 to about 5,000SCF/Bbl.
 33. The process of claim 21 wherein the atom ratio of theplatinum:iridium ranges from about 1:1 to about 2:1, and the atom ratioof iridium:palladium ranges from about 2:1 to about 10:1.